Laser sights are particularly effective as sighting devices because the lasers illuminate spots on their targets and do not require users to align an eye with a sighting device, which can limit or obscure the user's view of the targets or their surroundings. When mounted on firearms, the laser sights emit beams that are directed along the expected flight paths of projectiles discharged from the firearms. However, the laser sights are necessarily mounted offset from the firearm barrels, so the laser beams extend generally parallel but offset from the initial flight paths of the projectiles. At close distances, the offset can result in a significant targeting error approximating the initial offset. Small angular adjustments of the laser sights can compensate for the offset at longer distances.
Particularly for handguns, which are intended for targeting over shorter distances, reducing the amount of this offset is desirable. My earlier U.S. Pat. No. 4,934,086 describes mounting a laser sight within the recoil spring tube of a firearm. The spring tube mounting locates the laser sight close to the barrel, protects the laser sight from exposure to external jarring, and avoids the encumbrance of an external accessory. However, such built-in mounting locations are not available in all handguns, so laser sights have also been externally mounted from both conventional rails and special adapters.
Laser sight modules have been mounted from conventional accessory mounts, such as Picatinny rails, in the same way that scopes and other accessories have been mounted on firearms. Typically, the laser sight modules include receptors for engaging the accessory mounts on the firearms. For example, dovetail-type receptors have been formed in laser sight modules for engaging Picatinny rails on the firearms. Laser sight modules have been mounted from different types of accessory mounts on the firearms, including from other types of rails, using mating receptors and have also been mounted on firearms using clamping devices or other forms of attachment for engaging firearm barrels, frames, or other components that are not otherwise intended as accessory mounts.
Often, it is desirable to mount the laser sights so that the sights can be removed and transferred between firearms, generally with as little adjustment as possible. Again, rails, particularly Picatinny-type rails, have been used for this purpose. The rails can be formed integral with the firearm frames or clamped or otherwise attached to the firearm barrels or frames.
Both the accessory mounts presented on firearms and the receptors for engaging them tend to offset the laser sights from the barrels. Alternative adapter structures used for attaching laser sights to firearm components that are not otherwise arranged as mountings also tend to offset the laser sights from firearm barrels. Among the accessory mounts, rail mounts, such as Picatinny rails, offset laser sights by the space occupied by the rails themselves and any attachments for fixing the rails to the firearm barrels or frames. In addition, the receptors used for engaging the rails can take up more space and displace the laser sights farther from firearm barrels. The known laser sight modules mounted in this way are also exposed to jarring and can encumber the handling or operation of firearms, particularly as the laser sights are mounted at increasing offset from firearm barrels.